Abstract
Autoantibodies are produced within germinal centers (GC), in a process regulated by interactions between B, T follicular helper (Tfh), and T follicular regulatory (Tfr) cells. The GC dysregulation in human autoimmunity has been inferred from circulating cells, albeit with conflicting results due to diverse experimental approaches. We applied a consistent approach to compare circulating Tfr and Tfh subsets in patients with different autoimmune diseases. We recruited 97 participants, including 72 patients with Hashimoto's thyroiditis (HT, n = 18), rheumatoid arthritis (RA, n = 16), or systemic lupus erythematosus (SLE, n = 32), and 31 matched healthy donors (HD). We found that the frequency of circulating T follicular subsets differed across diseases. Patients with HT had an increased frequency of blood Tfh cells (p = 0.0215) and a reduced Tfr/Tfh ratio (p = 0.0338) when compared with HD. This was not observed in patients with systemic autoimmune rheumatic diseases (RA, SLE), who had a reduction in both Tfh (p = 0.0494 and p = 0.0392, respectively) and Tfr (p = 0.0003 and p = 0.0001, respectively) cells, resulting in an unchanged Tfr/Tfh ratio. Activated PD-1+ICOS+Tfh and CD4+PD-1+CXCR5-Tph cells were raised only in patients with SLE (p = 0.0022 and p = 0.0054), without association with disease activity. Our data suggest that GC dysregulation, assessed by T follicular subsets, is not uniform in human autoimmunity. Specific patterns of dysregulation may become potential biomarkers for disease and patient stratification.